The invention is directed to an illuminator for photodynamic therapy, including diagnosis. More specifically, the invention is directed to an illuminator for photodynamic therapy which produces a high-powered beam at the appropriate wavelengths which is highly uniform in both intensity and spectral characteristics (color) throughout the illuminated area.
Photodynamic therapy ("PDT") or photochemotherapy is currently being used to treat several types of aliments in or near the skin or other tissues. For example, PDT is being used to treat different types of skin cancer. In PDT, a patient is administered a photo-activable drug which accumulates in the tissue being treated. An area of the patient which includes the tissue being treated is then exposed to light. The light causes chemical and/or biological changes in the photo-activable drug which in turn selectively distinguishes, destroys or alters the target tissue while at the same time causing only mild and reversible damage to other tissues in the treatment area.
General background information on PDT using 5-Aminolevulinic acid ("ALA") can be fund in U.S. Pat. No. 5,079,262, entitled "Method of Detection and Treatment of Malignant and Non-Malignant Lesions Utilizing 5-Aminolevulinic Acid," and issued to James C. Kennedy et al. on Jan. 7, 1992 and U.S. Pat. No. 5,211,938, entitled "Method of Detection of Malignant and Non-Malignant Lesions by Photochemotherapy of Protoporphyrin IX Percursors," and issued to James C. Kennedy et al. on May 18, 1993. The contents of these patents are incorporated herein by reference. ALA is a drug which functions as a prodrug in the body and metabolizes to protoporphyrin IX ("PpIX"). PpIX in cells may be photoactivated with light of a certain wavelength to either fluoresce, degrade or otherwise be altered.
For therapeutic reasons it is desirable to have a large power output which is uniform in intensity and color over a large area. In addition, it has been discovered that use of light having wavelengths between about 600 nm (nanometers) and about 700 nm is particularly advantageous for certain forms of treatment.
Unfortunately, conventional illuminators produce a relatively high percentage of light in the infrared ("IR") region. In order to prevent this high percentage of infrared radiation from harming a patient, the overall power output of the lamp must be limited. Moreover, conventional illuminators do not produce a beam which is uniform in intensity and color over a large area, e.g., greater than 10 cm (centimeters) in diameter, and do not produce light virtually entirely in the 600 nm to 700 nm wavelength range.
Accordingly, there is a real need for an improved illuminator for photodynamic therapy.